Adjustable tensioning device for circular screens

ABSTRACT

There is disclosed a novel circular screen frame assembly comprised of a screen, a support ring and an annular clamping and tensioning assembly. In one embodiment of the present invention, the annular clamping and tensioning assembly is comprised of a clamping ring and a tensioning ring. The support ring is adapted to be positioned and held within the housing of the sifter assembly. The clamping ring circumferentially secures the screen to the tensioning ring with the resulting annular clamping and tensioning assembly being positioned about the support ring with adjustable fixing means. Tensioning of the circular screen is effected either by the horizontal or vertical displacement of the annular clamping and assembly with reference to the support ring about a plurality of points about the rings.

(451 Dec.4, 1973 ADJUSTABLE TENSIONING DEVICE FOR CIRCULAR SCREENS [75] Inventors: Edward S. Wright, Pittsburgh, Pa.;

John W. Angstadt; Otto C. Krolopp, both of Williamsville, N.Y.

[73] Assignee: Blaw-Knox Food and Chemical 7 Equipment, Inc., Buffalo, NY.

22 Filed: Apr. 30, 1973 21 Appl. No.: 355,916

US. Cl. 209/403, 209/404 B07b l/06 Field of Search 209/279, 280, 350, 209/351, 403, 404, 405, 408, 412, 413, 361; l08/l27.1, 128.1, 415.1; 140/109 FOREIGN PATENTS OR APPLICATIONS 399,628 3/1909 France 209/350 Primary ExaminerFrank W. Lutter Assistant Examiner-Ralph J. Hill Att0rney-Louis E. Mam et a1.

[ 5 7 ABSTRACT There is disclosed a novel circular screen frame assembly comprised of a screen, a support ring and an annular clamping and tensioning assembly. In one embodiment of the present invention, the annular clamping and tensioning assemblyis comprised of a clamping ring and a tensioning ring. The support ring is adapted to be positioned and held within the housing of the sifter assembly. The clamping ring circumferentially secures the screen to the tensioning ring with the resulting annular clamping and tensioning assembly being positioned about the support ring with adjustable fixing means. Tensioning of the circular screen is effected either by the horizontal or vertical displacement of the annular clamping and assembly with reference to the support ring about a plurality of points about the rings.

15 Claims, 7 Drawing Figures IIIIIIIIII PATENTEUDEC 4 1915 SHEET 10F 2 FIG.2

PATENTED 73 3.776.382 SHEET 20F 2 FIG.3

WEIQ .H.

FIG. 5

FIG. 4

FIG. 7

'1 ADJUSTABLE TENSIONING DEVICE FOR CIRCULAR SCREENS surface being generally referred to as the under sized or minus material. Screening machines or apparatus are provided with drive means to move the screening surface and may beclassified or divided into classes. generally according to the motion-thereof, i.e'.,'revolving screens, shaking'screens, vibrating screens, and oscillating screens. The present invention relates to screen ing assemblies having as a screening surface a woven material, such as wire, silk, cloth and the like.

A circular screening machine or apparatus is generally comprised of at least one circular screen frame or a plurality of circular screen frames having a permanently affixed screening surface of a desired mesh and face of a circular screen frame assembly of a circular screening apparatus.

SUMMARY OF THE INVENTION.

, These and other objects of the present invention are achieved by a novel circular screen frame assembly I comprised of a screen, a support ring and an annular clamping and tensioning assembly. In one embodiment .of the presentinvention, the annular clamping and tensioning assembly is comprised of a clamping ring and 'a tensioning ring. The support ring is adapted to be positioned and held within the housing of the sifter assembly. The clamping ring circumferentially secures the screen to the tensioning ring with the resulting annular clamping and tensioning assembly being positioned aboutthe support ring withadjustable fixing means. Tensioning of the circular screen is effected either by horizontal or vertical displacement of the. annular clamping and assembly with reference to the support ring about a plurality of points about the rings, as more fully hereinafterdiscussed.

positioned within the housing of a vessel thereby dividing same into a plurality of chambers. The particulate material to be classified is introduced into the housing of the vessel moving about a generally horizontal plane to cause the material to pass over the screen to effect size separation. The screen is tensioned during'construction and prior to positioning the screen frame within the housing of the vessel, and after a predetermined period of time the screen frame is withdrawn and returned to the manufacturer for re-screening or re-adjustment', if possible, of the screen tension, pro vided the screening surface is in satisfactory condition. Thus, it is necessary to provide a reserve of at least one screen frame assembly to minimize downtime of the v screening machine or apparatus since the tension of a screen on a screen frame is not readily re-adjustable.

In U. S. Pat. No. 2,864,500 to Miller and U. S. Pat.

No. 3,126,332 to Salete there are disclosed rectangular screen frame assemblieswhich may be tensioned on a rectangular screening assembly. It is readily apparent that the tensioning of. a rectangular screen along the according to such disclosures, however, such screen frame assemblies are not adapted to the tensioning of a screen positioned on a circular'screen frame wherein it is necessary to evenly distributethe forces-along-the axes of the filaments forming the screening surface where the filaments are not generally normal to the screen frame.

OBJECTS OF THE INVENTION An object of the present invention is to provide a novel circular screen frame assembly 'for a circular screening machine or apparatus.

Another object of the present invention is to provide horizontal and vertical axis of the mesh maybe effected a novel circular screen' frame assembly including a screen capable of being readily tensioned in situ or proximate to the screening apparatus.

A still further object of the present invention is to provide a novel ,method for tensioning a screening sur- DESCRIPTION OF THE DRAWINGS The invention will now be described with reference to the accompanying drawings wherein like numerals designate like parts throughout and wherein: i FIG. 1 is a plane view of a rotary screening apparatus, such as a sifter; A

FIG. 2 is an enlarged partial cross-sectional view of a circular screen frameassembly illustrating one embodiment of the present invention;

FIG. 3 is a partial top view of the circular screenframe assembly of FIG. 2; I FIG. 4 is an enlarged partial cross-sectional view of a circular screen frame assembly illustrating another embodiment of the present invention;

FIG. 5 is an enlarged cross-sectional view of a circular screen frame assembly illustrating still another embodiment of the present invention;

' FIG. 6 is an enlarged cross-sectional view of a circular screen frame assembly illustrating a still further embodiment of the present invention; and

. FIG. 7 is an enlarged partial cross-sectional view of a circular screen frame assembly illustrating another embodiment of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS Various other objects and advantages of the present invention will become apparent from the following detailed description of exemplary embodiments when taken with reference to the accompanying drawings,

withthe novel features being particularly pointed out in the appended claims.

Referring now to FIG. 1, there is illustrated a rotary sifter assembly, generally indicated as 10, and comprised of a domed cover 12, upper and lower cylindrical wall members 14 and 16, and a bottom 18. The cover 12 and bottom 18 are affixed to the cylindrical wall members 14 and 16, respectively, by means known tothose skilled in the art, such as by welding, to provide a pressure tight vessel. The upper and lower cylindrical wall members 14 and 16 are-fixedly positioned to each other by means of a replaceable clamping ring 20, as more fully hereinafter discussed.

The cover 12 is provided with a centrally located inlet conduit 22 adapted for connection to a source of particulate material to be classified with a suitable flexible coupling (not shown). The upper and lower cylindrical wall members l4 and ,16 are provided with outlet conduits 24 and 26, respectively. The outlet conduit 24 provides a means for withdrawing the oversizcd or plus portions of the particulate material whereas the outlet conduit 26 provides a means for withdrawing the undersized or minus portions of the particulate material. The screening apparatus is mounted to a gyratary drive assembly, generally indicated as 28, driven by a suitable drive means (not shown) and positioned on a support platform.

Referring now to FIGS. 2 and 3 illustrating a preferred embodiment of the present invention, there is provided a circular screen frame assembly, generally indicated as 32, and comprised of a screen 34, an L- shaped support ring 36, and a screen clamping and tensioning assembly, generally indicated as 38. The L- shaped support ring 36 is formed of a vertical leg 40 and a horizontal leg 42 having a plurality of evenly spaced orifices 44 formed thereabout, as more fully hereinafter discussed. The end portion of the horizontal leg 42 is positioned within outwardly extending flange portions 14a and 16a of cylindrical wall members l4 and 16, respectively, and is held in place by the replaceable clamping ring 20. An O-ring 46 is disposed between suchend portion of the horizontal leg 42 and the replaceable clamping ring to provide for a pressure tight apparatus. I

The screen clamping and tensioning assembly 38' is comprised of a tensioning ring 50 having a plurality of evenly spaced orifices 52 formed therein, and a clamping ring 54 having a plurality of evenly spaced tapped orifices 56, and a securing means, such as headed bolts 58 and self-locking nuts 60 positioned within the orifices in the tensioning and clamping rings 50 and 54. The tensioning ring 50 is formed with an inner gener ally J-shaped channel to receive the generally U-shaped outer surface of the clamping ring 54. The tensioning ring 50 is formed with a shorter leg 62 thereof having an inner tapered surface 64 to receive a tapered outer surface 66 of the clamping ring 54, as more fully hereinafter described.

Generally, the screen frame assembly 32 is assembled prior to positioning within the housing of the sifter l0. Accordingly, the circular shaped screen 34 is provided with a plurality of orifices (not shown) evenly spaced about the periphery thereof in coincident relationship to the orifices 56, 52 and 44 formed within the clamp ing ring 54, the tensioning ring 50 and the support ring 36, respectively. Bolts 58 are threaded into the tapped orifices 56 of the clamping ring 54 and the orifices of the screen 34 positioning about the threaded portion thereof. Thereafter, the orifices 52 of the tensioning ring 50 are positioned about the threaded portion of the bolts 58 and nuts 60 evenly threaded thereon to cause the clamping ring 54 to move into the J-shaped channel 8 of the retaining ring 50.

It is noted (particularly with respect to FIG. 2) that upon the first metal to metal contact between the clamping ring 54 and tensioning ring 50 which is effected at the left hand portion of the juncture therebetween that further tightening of the nuts 60 on the threaded portion of the bolts 58 causes the screen 34 to be pulled therebetween as a result of the action of the tapered surface 64 and 66 of the tensioning ring 64 and the clamping ring 54, respectively, about the tangential portions of the screen 34 as a result of the even tensioning of the filaments forming the screen 34. The next step of assembling the circular screen frame assembly, after securely tightening the nuts 60, is to insert the threaded portion of the bolts 58 within the orifices 44 formed in the horizontal leg 42 of the supporting ring 36 and securely threading the self-locking nuts 68 about the threaded portion of the bolt 58. Thereafter rotational force is applied to the bolts 68 with tension testing until the screen 34 is properly tensioncd. It will be appreciated that assembly of the screening frame 32 as well as tensioning of the screen 34 may be accomplished in an area proximate to the screening apparatus 10, as distinguished from circular screen frame assemblies of the prior art which are manufactured and tensioned in a separate facility generally remote from the screening apparatus. The screen frame assembly 32 is now ready for positioning within the screening apparatus 10.

- The horizontal leg 42 of the support ring 36 is positioned on the upper surface of the outwardly flanged portion 16a of the cylindrical wall 16, with an O-ring seal 46 being thereafter disposed about the outer portion of the horizontal leg 42. The upper cylindrical member 14 is thereafter positioned over the lower ey lindrical member 16 with the outwardly extending flange portion 14a of the member 14 being positioned about the top surface of the horizontal leg 42. A removable clamping ring 20 is fixedly positioned about the outwardly extending section formed by the legs 14a and 16a of the cylindrical section to form a pressure tight screening apparatus.

It will be readily appreciated that tensioning of the screen 34 of the circular screen frame assembly 32 may be readily effected after a predetermined on-line operation by removing the replaceable ring 20 and upper cylindrical member 14 of the assembly thereby permitting removal of the circular screen frame assembly 34. Tensioning of the screen 34 maybe readily effected proximate to the screening assembly on appropriate support forms. It is understood that the screen 34 may be tensioned in situ by the use of an alternate bolt and nut configuration as well as the alteration tapped and untapped orifices. For example by providing a capped screw head bolt 58 would permit the tensioning of the screen 34 while positioned within the screening assembly by turning the cap screws 58 thereby vertically adjusting theclamping and tensioning assembly 32 to provide in situ tensioning. It will be also noted that tensioning of the screen 34 is effected at the tangent points of the filaments forming the mesh thereby preventing the spreading of the mesh orifices at the points tangential to the upper portion of the upper leg 40 of the support ring 36. a

While the present invention has been described with reference to the use of a unitary clamping ring 54 and a unitary tensioning ring 50, it is understood that such rings may be formed of a plurality of sub-assemblies including joint connections which are disposed about the support ring 36 in a manner to provide an essentially unitary structure. It is noted that the upper surface of the shorter leg 62 of the tensioning ring 50 is lower than I the other leg thereof and is higher with reference to the outlet conduit 24, such that the screening surface is self-cleaning thereby preventing trapping of particulate material. It will be understood that the materials of construction for' the rings include metals, plastics or combination thereof, with plastics being generally prethe metals.

FIG. 4 is another embodiment of the present invention for a screen frame assembly, generally indicated as 432, including a sifting screen 434, support ring 436, and an annular clamping and tensioning assembly, generally indicated as 438. The support ring 436 is generally T-shaped having vertical leg 440 disposed generally intermediate with horizontal legs 442a and 442k. The vertical leg 440 is provided with a'plurality of evenly spaced and-tapped orifices 480 about the circumference thereof. The screen 434 is positioned over the vertical leg 440 of the support ring 436 between a clamping ring 45.4 which is affixed to the vertical leg ,440, such as by flat-headed screws 482. The horizontal leg 442a of the support ring 436 is provided with a plurality of evenly spaced tapped orifices 444. A tensioning ring 450 is disposed about the inner surface of the vertical leg 440' above the horizontal leg 442a and may be vertically displaced by a knurl-headed threaded fastener 484 threaded in the orifice 444 and held in place by a jam nut 486. Thus,- the screen 434 may be properly tensioned by selective turning of the threaded fasteners 458. v

FIG. 5 illustrates still another embodiment of the present invention of a circular screen frame assembly. generally indicated as 532, comprised of a sifting screen 534, a J-shaped support ring 536 and a screen clamping and tensioning assembly, generally indicated as 538. The support ring 536 is provided with a plurality of evenly spaced tapped orifices 544 and is comprised of a horizontal leg 542, a vertical leg 540 and a shortened horizontal leg 580 extending parallel to the leg 540. The screen 534 is disposed between the leg 542 of the support ring 536 and a clamping ring 554 affixed thereto bythreaded fasteners 582. A tensioning ring 550 of the hose clamp type is positioned about a portion of the screen disposed between the horizontal legs 542 and 580 of the support ring 536. Tensioning of the screen 534 is effected by tightening the draw v band (not shown) of the tensioning ring 550.

The embodiment of FIG. 6 is similar to the embodi ment of FIG. 4 except that the tensioning ring 650 is formed of an inflatable circular rubber tube and is posi tioned on a horizontal leg 642a of the support ring 636. Tensioning is effected by inflating the rubber tube.

The embodiment of FIG. 7 is similar to the embodiment of FIG. 5, except that a Z-shaped ring 790 is positioned about the support ring 736 and is affixed thereto by threaded fasteners 792 disposed within tapped orifices 794 evenly spaced about the leg 742 of the supmetals, plastics, and the like. It is understood that acombination of such materials is also contemplated, e.g., plastic coated metals.

While the invention has been described in connection with an exemplary embodiment thereof, it will be understood that many modifications will be readily apparent to those of ordinary skill in the art; and this application is intended to cover any adaptions or variations thereoffTh'erefore it is manifestly intended that this invention be only limited by the claims and the equivalents thereof.

What is claimed is:

l. A circular screen frame assembly for a circular screening assembly which comprises:

a support ring means;

a circular screen means; and

an annular clamping and tensioning means for posimeans and said tensioning ring means by a plurality threaded fasteners means and wherein said tensioning ring means is moved relative'to said support ring to effect tensioning of said screen member.

'thescreen means by said plurality of threaded fasteners disposed about the periphery of said ring means.

6. The assembly as defined .in claim 4 wherein said tensioning ring means is an inflatable tube means.

7. The assembly as defined in claim 2 wherein the upper surface of said ring means is above the lower portion of an oversized particulate outlet conduit.

8. The assembly as defined in claim 2 wherein a horizontal leg means of said support ring is positioned be-.

tween cylindrical side walls of said screening assembly rigidly affixed to one another by a removable clamping means. I

9. The assembly as defined in claim 8 wherein a gasket means is provided between the extended portion of said horizontal leg means and said removable clamping means. 4

10. The assembly as defined in claim 2 wherein said screen means is affixed to a leg means of said support ring means.

11. The assembly as defined in'claim 10 wherein said leg means of said support ring means is vertical leg 7 means thereof and is affixed by a plurality of threaded fastener means.

12. The assembly as defined in claim 1 1 wherein said tensioning ring means is movable in a plane normal to said screen means. I

13. The assembly as defined in claim 12-wherein said tensioning ring means is movably disposed with respect to said support ring in a plane parallel to said vertical leg means of said support ring. I

14. The assembly as defined in claim '10 wherein said leg means of said support ring means is a horizontal leg means thereof and is affixed by a plurality of threaded fastener means. I

15. The assembly as defined in claim 14 wherein said clamping ring means is disposed between said horizontal leg means of said support ring means and a vertically extending leg means therefor and said clamping ring means is radically adjustable. 

1. A circular screen frame assembly for a circular screening assembly which comprises: a support ring means; a circular screen means; and an annular clamping and tensioning means for positioning and adjustably tensioning said screen means about said support ring means.
 2. The assembly as defined in claim 1 wherein said annular clamping and tensioning means is comprised of a clamping ring means and a tensioning ring means.
 3. The assembly as defined in claim 2 wherein said screen means is affixed between said clamping ring means and said tensioning ring means by a plurality threaded fasteners means and wherein said tensioning ring means is moved relative to said support ring to effect tensioning of said screen member.
 4. The assembly as defined in claim 3 wherein said support ring includes an upwardly extending leg member means over which said screen means is disposed.
 5. The assembly as defined in claim 4 wherein selected portions of said clamping ring means and said tensioning ring means are moved in a plane normal to the screen means by said plurality of threaded fasteners disposed about the periphery of said ring means.
 6. The assembly as defined in claim 4 wherein said tensioning ring means is an inflatable tube means.
 7. The assembly as defined in claim 2 wherein the upper surface of said ring means is above the lower portion of an oversized particulate outlet conduit.
 8. The assembly as defined in claim 2 wherein a horizontal leg means of said support ring is positioned between cylindrical side walls of said screening assembly rigidly affixed to one another by a removable clamping means.
 9. The assembly as defined in claim 8 wherein a gasket means is provided between the extended portion of said horizontal leg means and said removable clamping means.
 10. The assembly as defined in claim 2 wherein said screen means is affixed to a leg means of said support ring means.
 11. The assembly as defined in claim 10 wherein said leg means of said support ring means is vertical leg means thereof and is affixed by a plurality of threaded fastener means.
 12. The assembly as defined in claim 11 wherein said tensioning ring means is movable in a plane normal to said screen means.
 13. The assembly as defined in claim 12 wherein said tensioning ring means is movably disposed with respect to said support ring in a plane parallel to said vertical leg means of said support ring.
 14. The assembly as defined in claim 10 wherein said leg means of said support ring means is a horizontal leg means thereof and is affixed by a plurality of threaded fastener means.
 15. The assembly as defined in claim 14 wherein said clamping ring means is disposed between said horizontal leg means of said support ring means and a vertically extending leg means therefor and said clamping ring means is radically adjustable. 